The present chapter covers the acquisition (and processing) literature related to null arguments (subjects and objects) in adult second language (L2) acquisition. We introduce the reader to the linguistic descriptions and relevant theories under which adult L2 acquisition of these domains have been couched and to which existing studies contribute. While we offer a summative view of a rather large literature, we provide details of some key studies, which serves to present and contextualize: (i) the historical landscape, (ii) what we have learned incrementally from relevant studies in their aggregate over several decades, and (iii) the variety of experimental methods and sub-questions that characterize this well-documented domain of L2 grammar.